Many industrial processes require a particular spatial relationship to be established between a plurality of parts. One common example pertains to industrial machining operations where a machine tool, such as a drill reamer, punch or tap must be aligned relative to a workpiece. Misalignment can result in poorly manufactured products and/or broken tools. In other situations, it is important to properly align a plurality of movable components with respect to a fixed frame of reference. For example, it may be necessary to align a plurality of turbine parts with respect to an axis of rotation, or to align an assembly of robotic arms with respect to a reference plane.
Until fairly recently, the tools available to industries for these alignment purposes consisted primarily of levels, feeler gauges, stretched piano wires, telescopes and such. In fact, these tools are still employed in many industries.
Some industries require precision that cannot readily be obtained with the prior art mechanical, electromechanical and optical alignment tools. For example, industries that have become highly automated rely upon the precise spatial and angular orientation of tools relative to one another and relative to workpieces. As noted above, improper alignment in these situations can result in high reject rates and tool breakages. Even a short down time for a highly automated transfer line can be extremely expensive.
The need for increased precision and for minimizing down time has made alignment systems employing light sources and accurate photoelectric targets a desirable approach for many industries. In particular, alignment devices employing laser light were developed some twenty years ago. The typical prior art laser alignment device comprises a laser emitter and an electronic target including at least one photocell that is responsive to produce electrical output signals capable of identifying locations of points at which the target is impinged upon by light. The target typically is operative to sense the center of energy of the laser light impinging thereon. Targets are available to provide accuracy within 0.0001 inch, which is a small fraction of the diameter of a human hair. In the typical application, the emitter and the target are positioned at predetermined locations relative to the industrialequipment to be aligned. Extremely precise adjustments then can be made to the alignment of the industrial equipment utilizing the output from the alignment system. Several very desirable variations of the above described alignment system have been developed. For example, U.S. Pat. No. 3,902,810 which issued to Martin R. Hamar on Sept. 2, 1975 is entitled SYSTEM AND METHOD FOR ALIGNING APPARATUS UTILIZING A LASER, and shows a laser system particularly effective for aligning members, such as turbine parts, along a particular axis. Another efficient laser alignment system is shown in U.S. Pat. No. 4,297,031 and U.S. Pat. No. 4,382,680, both of which issued to Martin R. Hamar and are entitled APPARATUS AND PROCESS FOR SWEEPING A FLAT OPTICAL LIGHT PLANE. Still another very efficient laser alignment system is shown in U.S. Pat. No. 4,566,202 which issued on Jan. 28, 1986 to Martin R. Hamar and is entitled LASER APPARATUS FOR EFFECTIVELY PROJECTING THE AXIS OF ROTATION OF A ROTATING TOOL HOLDER.
Most of the prior art laser alignment systems rely in part upon the accurate placement of the target relative to a desired measurement point. It follows, therefore, that a misplacement or misalignment of the target relative to the desired measurement point can offset the extreme accuracies that otherwise could be obtained with laser alignment systems. A particularly effective target to compensate for possible misalignment is shown in U.S. Pat. No. 4,483,618 which issued to Martin R. Hamar on Nov. 20, 1984 and is entitled LASER MEASUREMENT SYSTEM, VIRTUAL DETECTOR PROBE AND CARRIAGE YAW COMPENSATOR. Another prior art means for achieving stability and accuracy with a laser alignment system is shown in U.S. Pat. No. 4,045,129 which issued to Martin R. Hamar on Apr. 30, 1977 and is entitled APPARATUS FOR HARD MOUNTING AN OPTICAL MEMBER TO A RIGID BASE. The disclosures of the above identified United States Patents to Martin R. Hamar are incorporated herein by reference.
The photocells of the above described alignment targets typically are operative to sense the center of energy of light impinging thereon. Therefore, it is generally important to provide a laser emitter that will produce a stable and collimated beam of light. An unstable beam of light may have a center of energy that is substantially offset from the geometric center of the beam. Similarly, a laser emitter producing a beam that is misaligned or not properly collimated may give imprecise readings in certain applications. Many laser sources include complex and costly optical compensating devices incorporated therein. For example, U.S. Pat. No. 4,170,401 which issued to Yoder et al on Oct. 9, 1979, shows one such compensating system employing at least five optical components which are operative to first split the incoming beam, rotating the wavefront of one of the split portions of the beam and then recombining the two components. Other equally complex systems have been developed to stabilize light beams. The various optical members of such systems must be properly and securely mounted relative to one another and relative to the housing in which the laser source is disposed. Additionally, the precise positions at which the various optical members are disposed can be changed due to thermal expansion caused by the heat of the laser system itself. The mountings required for the optical members to prevent or offset the effects of thermal expansion also contribute to manufacturing expenses.
Recently, it has become desirable to achieve precise alignment of structural members which are disposed in a potentially explosive environment, such as an environment in which highly volatile fuels are used (e.g. missile launching or fueling stations). Prior art laser alignment systems which generate heat or which create a possibility of electrical short circuits generally can not be employed in these environments.
In view of the above, it is an object of the subject invention to provide an industrial alignment system that can efficiently produce a spatially stable light beam.
It is another object of the subject invention to provide an alignment system that substantially reduces and simplifies the optical components required therein.
It is another object of the subject invention to provide an alignment system wherein the heat generating portions thereof can be spaced from the light emitting portions thereof.
It is another object of the subject invention to provide a laser alignment system that can be manufactured with substantial cost savings.